Mannitol, intracranial pressure, and vasogenic edema.

The effect of a 2 g/kg intravenous bolus of mannitol on intracranial pressure (ICP) and white matter water content was determined by following the time course of ICP and spatial white matter water content after administration of mannitol in a hemispheric cold lesion model of vasogenic edema in the cat. After mannitol infusion, maximal ICP reduction occurred at approximately 20 minutes and began to return to baseline after 26 minutes. White matter water content in the control hemisphere began to decrease much later, reaching a minimum at 60 minutes. White matter water content in the lesioned hemisphere was not changed significantly after mannitol infusion. We conclude that the rapid reduction of ICP after intravenous administration of mannitol is not solely due to the dehydration of white matter.